Exhaust gas purification apparatus

ABSTRACT

An exhaust gas purification apparatus includes a honeycomb structure which has an introduction end face and an exhaust end face opposite to the introduction end face in the longitudinal direction of the honeycomb structure. A casing houses the honeycomb structure and has an introduction casing end face connected to an introduction pipe and an exhaust casing end face connected to an exhaust pipe. The introduction end face of the honeycomb structure faces the introduction casing end face. The exhaust end face of the honeycomb structure faces the exhaust casing end face. A holding sealing material is disposed between the honeycomb structure and the casing. A stopping member has a plurality of openings and covers the exhaust end face.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to PCTApplication No. PCT/JP2008/054405 filed Mar. 11, 2008, the contents ofwhich are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exhaust gas purification apparatus.

2. Discussion of the Background

Conventionally, exhaust gas discharged from an internal combustionengine such as a diesel engine contains particulate matter (alsoreferred to as PM hereafter), and in recent years, the harm that the PMcauses to the environment and the human body has become a problem. Theexhaust gas also contains harmful gas components such as CO, HC and NOx,and the harm that these harmful gas components cause to the environmentand the human body has become a further problem.

Therefore, various exhaust gas purification apparatuses for capturing PMcontained in exhaust gas and converting harmful gas components such asCO, HC and NOx contained in exhaust gas have been proposed. The exhaustgas purification apparatus of this kind includes a honeycomb structureformed from a porous ceramic such as cordierite and silicon carbide; acasing in which the honeycomb structure is disposed and which isconnected to an introduction pipe connected to an internal combustionengine, through which exhaust gas is introduced, and an exhaust pipeconnected to the outside, through which the exhaust gas is discharged;and a holding sealing material, which is disposed between the honeycombstructure and the casing to prevent a gap from being formed between thehoneycomb structure and the casing, and which holds the honeycombstructure.

However, in the exhaust gas purification apparatus of this kind,pressure (also referred to as exhaust gas pressure hereafter) is appliedto the honeycomb structure as the exhaust gas flows from theintroduction pipe side to the exhaust pipe side, and as a result, theentire honeycomb structure may move to the exhaust pipe side from itsinitial disposal position. In such a case, the honeycomb structurecollides with the casing such that the honeycomb structure is damaged,leading to a reduction in PM capture efficiency, a reduction in harmfulgas component purification efficiency, an increase in pressure loss, andso on. As a result, the purification performance of the honeycombstructure decreases dramatically.

In response to this problem, an exhaust gas purification apparatus thatprevents collisions between the honeycomb structure and the casing hasbeen proposed (JP 08-281034 A, JP 2000-45759 A).

JP 08-281034 A discloses an exhaust gas purification apparatus in whicha peripheral portion of an end face of a honeycomb structure is fixed bya fixing member disposed in a casing such that the honeycomb structureis held fixedly in the casing.

JP 2000-45759 A discloses an exhaust gas purification apparatus in whichan end portion of the casing is formed in a cone shape and thecone-shaped end portion of the casing is brought into contact with theperipheral portion of the end face of the honeycomb structure such thatthe honeycomb structure is held fixedly in the casing.

The contents of JP 08-281034 A and JP 2000-45759 A are incorporatedherein by reference in their entirety.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, an exhaust gaspurification apparatus includes at least one honeycomb structure, acasing housing, a holding sealing material, and a stopping member. Theat least one honeycomb structure includes a plurality of honeycomb firedbodies which are bound together via an adhesive layer and each of whichincludes cell walls extending along a longitudinal direction of the atleast one honeycomb structure to define cells. The at least onehoneycomb structure includes an introduction end face and an exhaust endface opposite to the introduction end face in the longitudinaldirection. The casing houses the at least one honeycomb structure andincludes an introduction casing end face and an exhaust casing end face.The introduction casing end face is connected to an introduction pipe tointroduce an exhaust gas, and the exhaust casing end face is connectedto an exhaust pipe to discharge the exhaust gas. The introduction endface of the at least one honeycomb structure faces the introductioncasing end face, and the exhaust end face of the at least one honeycombstructure faces the exhaust casing end face. The holding sealingmaterial is disposed between the at least one honeycomb structure andthe casing to hold the at least one honeycomb structure. The stoppingmember has a plurality of openings and disposed in the casing. Thestopping member covers the exhaust end face of the at least onehoneycomb structure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings.

FIG. 1 is a schematic cut-away perspective view showing an exhaust gaspurification apparatus according to the first embodiment of the presentinvention.

FIG. 2 is a schematic cross-sectional view showing a cross-section ofthe exhaust gas purification apparatus according to the first embodimentof the present invention cut parallel to a longitudinal direction.

FIG. 3 is a schematic perspective view showing the honeycomb filter ofthe exhaust gas purification apparatus according to the first embodimentof the present invention.

FIG. 4A is a schematic perspective view showing a honeycomb fired bodyof the honeycomb filter shown in FIG. 3, and

FIG. 4B is an A-A line cross-sectional view of the honeycomb fired bodyshown in FIG. 4A.

FIG. 5A is a schematic perspective view showing the stopping member ofthe exhaust gas purification apparatus according to the first embodimentof the present invention, and FIG. 5B is a schematic perspective viewshowing the holding sealing material of the exhaust gas purificationapparatus according to the first embodiment of the present invention.

FIG. 6 is a schematic perspective view showing a state in which thehoneycomb filter and the stopping member and holding sealing materialshown in FIGS. 5A and 5B are disposed in the casing to which theintroduction pipe and exhaust pipe according to the embodiment of thepresent invention are connected.

FIG. 7 is a schematic cross-sectional view showing a cross-section ofthe exhaust gas purification apparatus according to the secondembodiment of the present invention cut parallel to the longitudinaldirection.

FIG. 8A is a schematic perspective view showing the buffer member of theexhaust gas purification apparatus according to the second embodiment ofthe present invention, and FIG. 8B is a schematic perspective viewshowing the fixing member of the exhaust gas purification apparatusaccording to the second embodiment of the present invention.

FIG. 9 is a schematic perspective view showing a state in which thehoneycomb filter according to the embodiment of the present invention,the holding sealing material, the stopping member, and the buffer memberand fixing member shown in FIGS. 8A and 8B are disposed in the casing towhich the introduction pipe and exhaust pipe are connected.

FIG. 10A is a schematic perspective view showing a casing and a fixingmember of the exhaust gas purification apparatus according to the fourthembodiment of the present invention, and FIG. 10B is a schematic sideview showing the casing and the fixing member shown in FIG. 10A.

FIG. 11 is a schematic cross-sectional view showing a cross-section ofthe exhaust gas purification apparatus according to the seventhembodiment of the present invention cut parallel to the longitudinaldirection.

DESCRIPTION OF THE EMBODIMENTS

Embodiments will now be described with reference to the accompanyingdrawings, wherein like reference numerals designate corresponding oridentical elements throughout the various drawings.

An exhaust gas purification apparatus described according to theembodiment of the present invention includes a honeycomb structureformed by binding together a plurality of honeycomb fired bodies, inwhich a large number of cells separated by cell walls are disposed inparallel in a longitudinal direction, by interposing an adhesive layer;a casing to which an introduction pipe for introducing an exhaust gasand an exhaust pipe for discharging the exhaust gas are connected, thehoneycomb structure being disposed in the interior of the casing; aholding sealing material disposed between the honeycomb structure andthe casing for holding the honeycomb structure; and a stopping memberhaving a plurality of openings and disposed in the casing, wherein ofend faces of the honeycomb structure, at least an end face positioned onthe exhaust pipe side is covered by the stopping member.

In the exhaust gas purification apparatus according to the embodiment ofthe present invention, of the end faces of the honeycomb structure, atleast the end face positioned on the exhaust pipe side is covered by thestopping member.

Therefore, even when exhaust gas pressure is applied to the honeycombstructure, it is easy to prevent movement of a honeycomb fired body fromthe honeycomb structure to the exhaust pipe side. Moreover, even when ahoneycomb fired body moves, the moving honeycomb fired body is stoppedupon contact with the stopping member.

Hence, displacement and drop of the honeycomb fired bodies are morelikely to be prevented.

Note that in this description, the phrase “the exhaust pipe side endface of the aggregated honeycomb structure is covered by the stoppingmember” means that when seen from the exhaust pipe side, the entireexhaust pipe side end face of the aggregated honeycomb structureoverlaps the end face of the stopping member. In this case, the distance(shown by a double-headed arrow C in FIG. 2, to be described below)between the exhaust pipe side end face of the aggregated honeycombstructure and the end face of the stopping member is shorter than alongitudinal direction length (shown by a double-headed arrow D in FIG.2) of the honeycomb fired body. In other words, the exhaust pipe sideend face of the aggregated honeycomb structure and the end face of thestopping member are either removed from each other within a shorterrange than the longitudinal direction length of the honeycomb firedbody, or in contact with each other.

Furthermore, in this description, displacement of the honeycomb firedbody indicates a case in which a distance from the end face of theaggregated honeycomb structure to the end face of the projectinghoneycomb fired body is 5 mm or more.

In comparison with such an exhaust gas purification apparatus of thepresent embodiment, in the conventional exhaust gas purificationapparatus described in JP 08-281034 A, the honeycomb structure seems tobe held fixedly in the casing by a holding sealing material and thefixing member, and therefore collisions between the honeycomb structureand the casing seems to be prevented.

In the conventional exhaust gas purification apparatus described in JP2000-45759 A, the honeycomb structure seems to be held by a holdingsealing material and fixed by the contact between the cone-shaped endportion of the casing and the peripheral portion of the end face of thehoneycomb structure, and therefore collisions between the honeycombstructure and the casing seems to be prevented.

However, in the conventional exhaust gas purification apparatusesdescribed in JP 08-281034 A and JP 2000-45759 A, the following problemoccurs when a honeycomb structure (also referred to as an aggregatedhoneycomb structure hereafter) formed by binding together a plurality ofpillar-shaped honeycomb fired bodies, each of which includes a largenumber of cells disposed in parallel in a longitudinal direction andseparated by cell walls, by interposing an adhesive layer is used as thehoneycomb structure.

An aggregated honeycomb structure is manufactured by adhering aplurality of honeycomb fired bodies, each of which is formed by moldinga wet mixture into a predetermined shape and then firing the wetmixture, to each other using an adhesive, and then carrying out drying,solidifying, and so on. The strength of the dried and solidifiedadhesive layer is lower than that of the honeycomb fired body.Therefore, when exhaust gas pressure is applied to the aggregatedhoneycomb structure, cracks may form in the adhesive layer.

When a regenerating process or the like for removing PM is carried outwhile the adhesive layer is cracked, the crack may develop due tothermal shock, causing the adhesive layer to break, and as a result, apart of the honeycomb fired bodies bound together by the crackedadhesive layer may be pushed and moved toward the exhaust pipe side fromthe aggregated honeycomb structure. When the honeycomb fired body movesdramatically (also referred to hereafter as displacement of thehoneycomb fired body), a reduction in the purification performance ofthe aggregated honeycomb structure is more likely to occur. Furthermore,when the moved honeycomb fired body is pushed out of the aggregatedhoneycomb structure, the honeycomb fired bodies may come off.

As above described, displacement and coming off of the honeycomb firedbodies may occur in the conventional exhaust gas purificationapparatuses described in JP 08-281034 A and JP 2000-45759 A.

In the exhaust gas purification apparatus according to the embodiment ofthe present invention, a fixing member used for fixing the stoppingmember is desirably disposed in the casing.

In such an exhaust gas purification apparatus, the stopping member isless likely to shift from its initial disposal position.

Hence, even when exhaust gas pressure is applied to the honeycombstructure, movement of a honeycomb fired body from the honeycombstructure to the exhaust pipe side is more likely to be preventedreliably. Moreover, even when a honeycomb fired body moves, the movinghoneycomb fired body is stopped reliably upon contact with the stoppingmember. As a result, displacement and drop of the honeycomb fired bodiesis more likely to be prevented efficiently.

In the exhaust gas purification apparatus according to the embodiment ofthe present invention, the stopping member is desirably joined to thefixing member.

In such an exhaust gas purification apparatus, the stopping member isless likely to shift from its initial position. Accordingly, contact isunlikely to occur between the stopping member and the end face (exhaustpipe side end face) of the honeycomb structure.

Hence, damage such as chips and cracks is more likely to be preventedfrom occurring on the end face (exhaust pipe side end face) of thehoneycomb structure on which damage is particularly likely to occur.

As a result, a reduction in the purification performance of thehoneycomb structure is more likely to be prevented.

In the exhaust gas purification apparatus according to the embodiment ofthe present invention, the stopping member is desirably joined to thecasing.

In such an exhaust gas purification apparatus, the stopping member isless likely to shift from its initial disposal position.

Hence, even when exhaust gas pressure is applied to the honeycombstructure, movement of a honeycomb fired body from the honeycombstructure to the exhaust pipe side is more likely to be prevented.Moreover, even when a honeycomb fired body moves, the moving honeycombfired body is stopped upon contact with the stopping member. As aresult, displacement and drop of the honeycomb fired bodies is morelikely to be prevented efficiently.

In the exhaust gas purification apparatus according to the embodiment ofthe present invention, a buffer member is desirably disposed between thehoneycomb structure and the stopping member.

In such an exhaust gas purification apparatus, the exhaust pipe side endface of the honeycomb structure contacts the buffer member having abuffering function, and therefore, even when exhaust gas pressure isapplied such that the entire honeycomb structure moves from its initialdisposal position to the exhaust pipe side, shock such as vibration isunlikely to be applied to the exhaust pipe side end face of thehoneycomb structure.

Hence, in the exhaust gas purification apparatus according to theembodiment of the present invention, damage is more likely to beprevented from occurring on the end face (exhaust pipe side end face) ofthe honeycomb structure on which damage is particularly likely to occur.

As a result, a reduction in the purification performance of thehoneycomb structure is more likely to be prevented efficiently.

In the exhaust gas purification apparatus according to the embodiment ofthe present invention, the honeycomb structure is desirably a honeycombfilter in which one of end portions of each of the cells is sealed.

With such an exhaust gas purification apparatus, it is possible toremove PM contained in the exhaust gas.

In the exhaust gas purification apparatus according to the embodiment ofthe present invention, a catalyst is desirably supported on thehoneycomb filter (honeycomb structure).

In such an exhaust gas purification apparatus, during a regeneratingprocess, it is possible to reduce the activation energy required to burnthe PM captured in the honeycomb filter through contact between the PMand the catalyst. As a result, the captured PM is more likely to beburned at a lower temperature. Moreover, by bringing the catalyst intocontact with harmful gas components such as CO, HC and NOx contained inthe exhaust gas, these harmful gas components contained in the exhaustgas are more likely to be converted.

In the exhaust gas purification apparatus according to the embodiment ofthe present invention, the honeycomb structure may be a catalystsupporting carrier in which the one of end portions of each of the cellsis not sealed, and a catalyst may be supported on the catalystsupporting carrier.

With such an exhaust gas purification apparatus, harmful gas componentssuch as CO, HC and NOx contained in the exhaust gas are more likely tobe converted by bringing the catalyst into contact with these harmfulgas components contained in the exhaust gas.

In the exhaust gas purification apparatus according to the embodiment ofthe present invention, it is desirable that a plurality of honeycombstructures are disposed in the casing, and of end faces of each of thehoneycomb structures, at least an end face positioned on the exhaustpipe side is desirably covered by the stopping member.

In such an exhaust gas purification apparatus, movement of a part of thehoneycomb fired bodies of one honeycomb structure to the exhaust pipeside is more likely to be prevented even when exhaust gas pressure isapplied. Moreover, even when a honeycomb fired body moves, the movinghoneycomb fired body is stopped upon contact with the stopping member.Hence, a part of the honeycomb fired bodies of the one honeycombstructure is never pushed out to the exhaust pipe side. Accordingly, thehoneycomb fired body is unlikely to collide with another honeycombstructure disposed downstream of the one honeycomb structure, andtherefore damage to the another honeycomb structure is more likely to beprevented. As a result, a reduction in the purification performance ofthe another honeycomb structure is more likely to be prevented.

In the exhaust gas purification apparatus according to the embodiment ofthe present invention, it is desirable that the plurality of honeycombstructures include at least one honeycomb filter and at least onecatalyst supporting carrier and the catalyst supporting carrier isdisposed further toward the introduction pipe side than the honeycombfilter.

In such an exhaust gas purification apparatus, heat generated when thecatalyst supporting carrier converts harmful gas components contained inthe exhaust gas is likely to be used easily during PM combustion in thehoneycomb filter positioned downstream of the catalyst supportingcarrier. Hence, with the exhaust gas purification apparatus according tothe embodiment of the present invention, PM contained in the exhaust gasis more likely to be removed extremely efficiently.

In the exhaust gas purification apparatus according to the embodiment ofthe present invention, a distance between an end face of the honeycombstructure and an end face of the stopping member is desirably less thanabout 1 mm.

In such an exhaust gas purification apparatus, when exhaust gas pressureis applied such that a part of the honeycomb fired bodies of thehoneycomb structure is pushed out to the exhaust pipe side, thepushed-out honeycomb fired body does not project from the end face ofthe honeycomb structure to the exhaust pipe side by about 1 mm or more.

Hence, with the exhaust gas purification apparatus according to theembodiment of the present invention, a reduction in purificationperformance due to displacement of the honeycomb fired body is likely tobe prevented more efficiently.

First Embodiment

A first embodiment serving as an embodiment of the present inventionwill be described below using the drawings.

FIG. 1 is a schematic cut-away perspective view showing an exhaust gaspurification apparatus according to the first embodiment of the presentinvention.

FIG. 2 is a schematic cross-sectional view showing a cross-section ofthe exhaust gas purification apparatus according to the first embodimentof the present invention cut parallel to a longitudinal direction.

Note that in the first embodiment, a honeycomb filter is used as anaggregated honeycomb structure.

As shown in FIGS. 1 and 2, in an exhaust gas purification apparatus 10according to the first embodiment of the present invention, the interiorof a cylindrical casing 30, to which an introduction pipe 20 a throughwhich exhaust gas discharged from an internal combustion engine isintroduced and an exhaust pipe 20 b through which the exhaust gas isdischarged to the outside after passing through the exhaust gaspurification apparatus are connected, is provided with a honeycombfilter 40, a holding sealing material 50 disposed between the honeycombfilter 40 and the casing 30 to hold the honeycomb filter 40, and astopping member 60 that covers an end face (also referred to as anexhaust pipe side end face hereafter) of the honeycomb filter 40positioned on the exhaust pipe 20 b side, has a plurality of openings 60a, and is joined to the casing 30.

Further, a distance C (see FIG. 2) between the exhaust pipe side endface 40 a of the honeycomb filter 40 and an end face of the stoppingmember 60 is less than about 1 mm.

A joint portion 60 b mainly including metal is provided near theperiphery of the stopping member 60, and by welding the joint portion 60b to the casing 30, the stopping member 60 and the casing 30 are joinedto each other (in FIG. 2, the welded part between the joint portion 60 band the casing 30 is indicated by 61).

A case in which exhaust gas passes through the exhaust gas purificationapparatus 10 having the configuration described above will be describedbelow using FIG. 2.

As shown in FIG. 2, exhaust gas introduced through the introduction pipe20 a (in FIG. 2, the exhaust gas is indicated by G1 and the flow of theexhaust gas is indicated by arrows) flows into one cell 45 that opensonto an end face 40 b of the honeycomb filter 40 positioned on theintroduction pipe side, and passes through a cell wall 46 separating thecell 45. At this time, PM in the exhaust gas is captured in the cellwall 46, and as a result, the exhaust gas is purified. The purifiedexhaust gas flows out through another cell 45 opening onto the exhaustpipe side end face 40 a, passes through the opening 60 a in the stoppingmember 60, and is discharged to the outside through the exhaust pipe 20b.

In the exhaust gas purification apparatus 10 of the first embodiment ofthe present invention, PM contained in the exhaust gas is purified inthe manner described above. At the same time, however, pressuregenerated by the exhaust gas G1 is applied to the honeycomb filter 40.

The honeycomb filter and each member forming the exhaust gaspurification apparatus 10 will be described below using the drawings.

First, the honeycomb filter 40 will be described using FIGS. 3, 4A and4B.

FIG. 3 is a schematic perspective view showing the honeycomb filter ofthe exhaust gas purification apparatus according to the first embodimentof the present invention.

FIG. 4A is a schematic perspective view showing a honeycomb fired bodyof the honeycomb filter shown in FIG. 3, and

FIG. 4B is an A-A line cross-sectional view of the honeycomb fired bodyshown in FIG. 4A.

As shown in FIG. 3, in the honeycomb filter 40, a plurality of honeycombfired bodies 41 such as that shown in FIG. 4A are bound together byinterposing an adhesive layer 42 to form a ceramic block 43, and a coatlayer 44 is formed on the periphery of the ceramic block 43.

Further, as shown in FIG. 4B, in the honeycomb fired body 41, a largenumber of cells 45 separated by cell walls 46 are disposed in parallelin a longitudinal direction (indicated in FIG. 4A by a double-headedarrow B), and one of end portions of each cell 45 is sealed by a plug47. Thus, the cell wall 46 functions as a filter.

Next, the stopping member, holding sealing material, casing,introduction pipe, and exhaust pipe will be described using FIGS. 5A, 5Band 6.

FIG. 5A is a schematic perspective view showing the stopping member ofthe exhaust gas purification apparatus according to the first embodimentof the present invention, and

FIG. 5B is a schematic perspective view showing the holding sealingmaterial of the exhaust gas purification apparatus according to thefirst embodiment of the present invention.

FIG. 6 is a schematic perspective view showing a state in which thehoneycomb filter and the stopping member and holding sealing materialshown in FIGS. 5A and 5B are disposed in the casing to which theintroduction pipe and exhaust pipe according to the embodiment of thepresent invention are connected.

First, the stopping member 60 will be described. As shown in FIG. 5A,the stopping member 60 is disc-shaped and includes wire mesh formed byknitting a metal wire 60 c having a predetermined wire diameter.Further, the diameter of an end face of the stopping member 60 issubstantially identical to an inner diameter of the casing 30 shown inFIG. 6. The plurality of openings (apertures) 60 a, which have aquadrangular shape when seen from above, are formed over substantiallythe entire end face, and each opening 60 a penetrates from one end faceof the stopping member 60 to the other end face thereof.

The size of the opening 60 a is sufficiently larger than that of thecells on a perpendicular cross-section to the longitudinal direction ofthe honeycomb fired body of the honeycomb filter 40.

Further, the joint portion 60 b mainly including metal is provided nearthe periphery of the stopping member 60.

An aperture ratio of the stopping member 60 is preferably at least about65% and at most about 95%, and more preferably in the range of about 70%to about 90%.

When the aperture ratio is about 65% or more, the exhaust gas tends topass easily and pressure loss is less likely to be increased.

When the aperture ratio is about 95% or less, on the other hand,strength is more likely to be ensured. As a result, when a honeycombfired body or the entire honeycomb filter is moved to the exhaust pipeside by the exhaust gas pressure, it may become easier to stop thehoneycomb fired body or the entire honeycomb filter reliably.

When the aperture ratio is in the range of about 70% to about 90%, theexhaust gas passes more easily, and therefore pressure loss is morelikely to be reduced. Moreover, sufficient strength is more likely to beensured, and therefore the honeycomb fired body or the entire honeycombfilter is more likely to be stopped more reliably.

Next, the holding sealing material 50 will be described. The holdingsealing material 50 shown in FIG. 5B mainly includes inorganic fiberssuch as alumina fibers, and has a substantially rectangular outer shape.The length of the holding sealing material 50 (indicated by adouble-headed arrow L in FIG. 5B) is substantially identical to thelength of the periphery of the honeycomb filter 40 shown in FIG. 6, andthe width (indicated by a double-headed arrow W in FIG. 5B) issubstantially identical to the longitudinal direction length of thehoneycomb filter 40. Further, the holding sealing material 50 has apredetermined thickness (indicated by a double-headed arrow T in FIG.5B).

Of the end faces of the holding sealing material 50 that are parallel tothe width direction, a projected portion 50 a is provided on one endface and a recessed portion 50 b is provided on the other end face. Theprojected portion 50 a and the recessed portion 50 b are formed to fittogether when the holding sealing material 50 is wrapped around theperiphery of the honeycomb filter 40, as shown in FIG. 6.

Next, the casing 30 will be described. The casing 30 shown in FIG. 6 isa so-called clamshell-type casing having a cylindrical shape and formedmainly by a metal such as stainless steel. More specifically, the casing30 is formed from two casing divided bodies 30 a and 30 b, each of whichhas a U-shaped cross-section obtained by dividing the casing 30 parallelto the longitudinal direction thereof, and includes an inner face 31 a(31 b) and an outer face 32 a (32 b). An inner diameter of the casing 30is slightly shorter than a length obtained by combining the diameter ofthe end face of the honeycomb filter 40 and the thickness of the holdingsealing material 50 when wrapped around the honeycomb filter 40, and thelength of the casing 30 is slightly greater than the longitudinaldirection length of the honeycomb filter 40.

Finally, the introduction pipe 20 a and exhaust pipe 20 b will bedescribed.

The introduction pipe 20 a mainly includes a metal such as stainlesssteel, and takes a cylindrical shape. As shown in FIG. 6, an outerdiameter (inner diameter) of one end face is substantially identical tothe outer diameter (inner diameter) of the casing 30. The outer diameter(inner diameter) of the other end face is smaller than the outerdiameter (inner diameter) of the end face of the casing 30. Further, inthe neighborhood of one end face, the introduction pipe 20 a takes atapered shape that decreases the diameter from one end face side towardthe other end face side.

If necessary, the other end face of the introduction pipe 20 a isconnected to the internal combustion engine via an exhaust gas pipefurther connected to the introduction pipe 20 a.

The exhaust pipe 20 b is configured similarly to the introduction pipe20 a, except that the other end face is connected to the outside.

A method for manufacturing the exhaust gas purification apparatusaccording to the first embodiment of the present invention will now bedescribed.

First, a method for manufacturing the honeycomb filter will bedescribed.

First, silicon carbide powders each having a different average particlediameter are mixed, and an organic binder such as carboxymethylcellulose and a dispersion medium such as water are added thereto andthen kneaded, whereupon a plasticizer such as glycerin, a lubricant suchas polyoxyethylene monobutyl ether, a forming auxiliary such as ethyleneglycol, and so on are added and kneaded to form a wet mixture. Extrusionmolding is then carried out using the wet mixture to manufacture a rawmolded body.

Next, the raw molded body is dried and then a paste having a similarcomposition to the raw molded body described above is filled into apredetermined cell of a ceramic dried body, whereupon drying anddegreasing are carried out. Firing is then carried out, and thus ahoneycomb fired body of a predetermined size, in which one of endportions of each cell is sealed, is manufactured.

Next, using a heat-resistant adhesive paste containing inorganic fiberssuch as alumina fibers, inorganic particles such as silicon carbidepowder, an inorganic binder such as silica sol, an organic binder suchas carboxymethyl cellulose, water, and so on, a large number of thehoneycomb fired bodies described above are bound together and thendried, hardened, and cut to manufacture a ceramic block.

Next, inorganic fibers including alumina silicate or the like, inorganicparticles such as silicon carbide powder, an inorganic binder such assilica sol, an organic binder such as carboxymethyl cellulose, water,and so on are kneaded to prepare a sealing material paste (a coat layerpaste).

Using the sealing material paste (coat layer paste) described above, asealing material layer (coat layer) is formed on the periphery of theceramic block, whereupon the sealing material layer (coat layer) isdried, resulting in manufacturing of a honeycomb filter taking the formof a round pillar-shaped aggregated honeycomb structure, in which one ofend portions of each cell is sealed.

Next, a mat material mainly including inorganic fibers such as aluminafibers is cut to manufacture a holding sealing material having asubstantially rectangular shape of a predetermined size, in which, ofthe end faces thereof that are parallel to the width direction, aprojected portion is formed on one end face and a recessed portionhaving a shape that fits the projected portion is formed on the otherend face.

Further, wire mesh is manufactured by cutting wire mesh having apredetermined mesh, wire diameter, and aperture ratio into a disc shapesuch that the diameter of an end face thereof is substantially identicalto the inner diameter of the casing. Next, a joint member having anouter diameter that is substantially identical to the inner diameter ofthe casing and an inner diameter that is substantially identical to thediameter of the end face of the honeycomb filter is manufactured bycarrying out a punching process on a disc-shaped metal plate mainlyincluding a metal such as stainless steel. This joint member is placedover the disc-shaped wire mesh and then welded to the wire mesh, wherebya stopping member formed with a joint portion is manufactured.

A method for manufacturing an exhaust gas purification apparatus usingthe honeycomb filter and the various members described above will now bedescribed.

First, the holding sealing material is wrapped around the periphery ofthe honeycomb filter such that the recessed portion and projectedportion of the holding sealing material are fitted together. Next, afirst casing divided body is disposed such that the inner face thereofis oriented upward, and the honeycomb filter wrapped in the holdingsealing material is disposed on the inner face of the first casingdivided body. Further, the stopping member is disposed adjacent to oneend face of the honeycomb filter. At this time, the stopping member isdisposed such that, of the end faces thereof, the end face not formedwith the joint portion is disposed on the honeycomb filter side.

Thus, the respective lower halves of the honeycomb filter and thestopping member are disposed on the first casing divided body.

Next, a second casing divided body is placed on the respective upperhalves of the honeycomb filter and the stopping member disposed on thefirst casing divided body, whereupon the casing divided bodies arecompressed from a vertical direction. Once the casing divided bodiescome into contact, the casing divided bodies are joined by welding toform the casing. Note that a joining device such as a screw or apredetermined fitting may be used instead of welding.

Next, the casing is joined to the joint portion of the stopping memberby welding. Note that a joining device such as a screw or apredetermined fitting may be used instead of welding.

Next, the exhaust pipe is connected to the end portion of the casingthat is positioned on the stopping member disposal side by welding.Similarly, the introduction pipe is connected to the end portion of thecasing on the opposite side to the exhaust pipe connection side.

Through the processes described above, the exhaust gas purificationapparatus according to the first embodiment of the present invention ismanufactured.

Effects of the exhaust gas purification apparatus according to the firstembodiment of the present invention will be cited below.

(1) In the exhaust gas purification apparatus according to the firstembodiment of the present invention, the exhaust pipe side end face ofthe honeycomb filter is covered by the stopping member.

Therefore, in a case where the exhaust pipe side end face of thehoneycomb filter and the end face of the stopping member come intocontact, it is easier to prevent a honeycomb fired body from moving tothe exhaust pipe side from the honeycomb filter even when exhaust gaspressure is applied to the honeycomb filter.

Further, in a case where the exhaust pipe side end face of the honeycombfilter and the end face of the stopping member are disposed at a remove,the honeycomb fired body is stopped upon contact with the stoppingmember even when a honeycomb fired body moves.

Hence, in the exhaust gas purification apparatus according to the firstembodiment of the present invention, the honeycomb fired body is notdisplaced from the honeycomb filter to the exhaust pipe side. Moreover,the honeycomb fired body is not pushed out from the honeycomb filter,and therefore drop of the honeycomb fired body is more likely to beprevented.

Note that when exhaust gas pressure is applied to the honeycomb filter,the entire honeycomb filter may move from its initial disposal positionto the exhaust pipe side. As described above, however, the exhaust pipeside end face of the honeycomb filter is covered by the stopping member.Therefore, in a case where the exhaust pipe side end face of thehoneycomb filter and the end face of the stopping member are disposed incontact with each other, the honeycomb filter is more likely to bereliably prevented from moving to the exhaust pipe side.

Furthermore, in a case where the exhaust pipe side end face of thehoneycomb filter and the end face of the stopping member are disposed ata remove, the exhaust pipe side end face of the moving honeycomb filtercomes into contact with the stopping member such that the entirehoneycomb filter is stopped even when the entire honeycomb filter movesto the exhaust pipe side. Thus, collisions between the honeycomb filterand the casing are more likely to be prevented, and as a result, damageto the entire honeycomb filter is more likely to be prevented.

(2) In the exhaust gas purification apparatus according to the firstembodiment of the present invention, the stopping member is joined to apredetermined position in the casing such that the stopping member isunlikely to shift from its initial disposal position. Therefore, evenwhen exhaust gas pressure is applied to the honeycomb filter, ahoneycomb fired body is more likely to be prevented from moving from thehoneycomb filter to the exhaust pipe side. Moreover, even when ahoneycomb fired body moves, the moving honeycomb fired body is stoppedupon contact with the stopping member. Hence, displacement and drop ofthe honeycomb fired bodies are more likely to be prevented efficiently.

(3) In the exhaust gas purification apparatus according to the firstembodiment of the present invention, the distance between the end faceof the honeycomb filter and the end face of the stopping member is lessthan about 1 mm, and therefore a pushed-out honeycomb fired body doesnot project from the end face of the honeycomb filter toward the exhaustpipe side by about 1 mm or more.

Hence, a reduction in the purification performance caused bydisplacement of the honeycomb fired body is more likely to be preventedeven more efficiently.

EXAMPLES

Specific examples of the first embodiment of the present invention areillustrated below. However, the first embodiment is not limited to theseexamples alone.

Example 1 (1) Manufacture of Honeycomb Filter (1-1) Raw Molded BodyManufacturing Process

An amount of 60% by weight of α-type silicon carbide powder having anaverage particle diameter of 11 μm and 40% by weight of α-type siliconcarbide powder having an average particle diameter of 0.5 μm were mixed.To 100 parts by weight of the obtained mixture were added 5 parts byweight of an organic binder (carboxymethyl cellulose) and 10 parts byweight of water serving as a dispersion medium and then kneaded. Smallamounts of a plasticizer (glycerin) and a lubricant (UNILUB,manufactured by NOF Corp.) were then added and kneaded to form a wetmixture, whereupon extrusion molding was carried out to manufacture araw molded body.

(1-2) Honeycomb Fired Body Manufacturing Process

Next, the raw molded body was dried using a microwave drying apparatusor the like to form a ceramic dried body, whereupon a paste having asimilar composition to the raw molded body was filled into apredetermined cell. Drying was then carried out again using the dryingapparatus, whereupon degreasing was carried out at 400° C. and firingwas carried out for three hours at 2200° C. in a normal-pressure argonatmosphere. As a result, a honeycomb fired body having a porosity of42%, an average pore diameter of 9 μm, a size of 34.3 mm×34.3 mm×150 mm,a cell density of 23.3 pcs/cm², and a cell wall thickness of 0.4 mm wasmanufactured.

(1-3) Ceramic Block Manufacturing Process

A large number of the honeycomb fired bodies were bound using aheat-resistant adhesive paste containing 30% by weight of alumina fibershaving an average fiber length of 20 μm, 21% by weight of siliconcarbide powder having an average particle diameter of 0.6 μm, 15% byweight of silica sol (SiO₂ solids content: 30% by weight), 5.6% byweight of carboxymethyl cellulose, and 28.4% by weight of water. Thebound honeycomb fired bodies were dried at 120° C. and then cut using adiamond cutter to manufacture a round pillar-shaped ceramic block.

(1-4) Sealing Material Paste Manufacturing Process

Next, 23.3% by weight of ceramic fibers (average fiber length: 50 μm)including alumina silicate, 30.2% by weight of silicon carbide powderhaving an average particle diameter of 0.3 μm, 7% by weight of silicasol (SiO₂ solids content: 30% by weight), 0.5% by weight ofcarboxymethyl cellulose, and 39% by weight of water were kneadedtogether to prepare a sealing material paste.

(1-5) Sealing Material Layer Formation Process

Next, a sealing material layer having a thickness of 0.2 mm was formedon the periphery of the ceramic block using the sealing material paste.The sealing material layer was then dried at 12° C. to manufacture ahoneycomb filter taking the form of a round pillar-shaped aggregatedhoneycomb structure of diameter 143.8 mm×length 150 mm, in which one ofend portions of each cell was sealed.

(2) Manufacture of Holding Sealing Material

A non-expansive alumina fiber mat (MAFTEC, manufactured by MitsubishiChemical Corp.) was cut to manufacture a holding sealing material at asize of length 452 mm×width 150 mm×thickness 8 mm, in which a projectedportion was formed on one of the end faces parallel to the widthdirection and a recessed portion shaped to fit into the projectedportion was formed in a part of the other end portion.

(3) Manufacture of Stopping Member

Disc-shaped wire mesh having a diameter of 152 mm was manufactured bycutting 16-mesh (the “mesh” represents the number of openings in 1 inch(25.4 mm)) plain weave wire mesh having a wire diameter of 0.2 mm and anaperture ratio of 76.6%. Further, a joint member of outer diameter 152mm (inner diameter 143.8 mm)×thickness 4 mm was manufactured by carryingout a punching process on a disc-shaped metal plate mainly including ametal such as stainless steel. The joint member was then placed over thedisc-shaped wire mesh and welded to the wire mesh, whereby a stoppingmember formed with a joint portion was manufactured.

(4) Manufacture of Exhaust Gas Purification Apparatus

The holding sealing material manufactured in Process (2) was wrappedaround the periphery of the honeycomb filter manufactured in Process (1)such that the recessed portion and projected portion fitted together.Next, a first stainless steel casing divided body having a U-shapedcross-section and including an inner face and an outer face was preparedby dividing a cylindrical body mainly including stainless steel or thelike parallel to the longitudinal direction, and the first casingdivided body was disposed such that the inner face of the first casingdivided body was oriented upward. In this state, the honeycomb filterwrapped in the holding sealing material was disposed on the inner faceof the first casing divided body.

Next, the stopping member manufactured in Process (3) was disposedadjacent to one end face of the honeycomb filter. At this time, thestopping member was disposed such that, of the end faces of the stoppingmember, the end face not formed with the joint portion was provided onthe honeycomb filter side.

Next, a second casing divided body was placed on the first casingdivided body provided with the honeycomb filter and the stopping member,whereupon the casing divided bodies were compressed from a verticaldirection. When the casing divided bodies came into contact, the casingdivided bodies were joined by welding to form a casing. Further, thecasing was joined to the joint portion of the stopping member bywelding.

Next, an exhaust pipe including stainless steel and formed in a taperedshape was disposed on the end portion of the casing on the stoppingmember disposal side and connected to the end portion of the casing bywelding. Similarly, an introduction pipe shaped identically to theexhaust pipe was connected to the end portion of the casing on theopposite side to the exhaust pipe connection side.

Through the processes described above, the exhaust gas purificationapparatus according to Example 1 was manufactured.

Note that in the exhaust gas purification apparatus manufactured in thismanner, the distance between the exhaust pipe side end face of thehoneycomb filter and the end face of the stopping member was 0.5 mm.

In the exhaust gas purification apparatus of Example 1, the exhaust pipeside end face of the honeycomb filter is covered by the stopping memberand the stopping member is joined to a predetermined position in thecasing, and therefore the stopping member is unlikely to shift from itsinitial disposal position. It may therefore be assumed that even whenexhaust gas pressure is applied, displacement and drop of the honeycombfired bodies can be prevented efficiently.

Furthermore, the distance between the end face of the honeycomb filterand the end face of the stopping member is less than about 1 mm. It maytherefore be assumed that a reduction in the purification performance ofthe honeycomb filter can be prevented efficiently.

Second Embodiment

A second embodiment serving as an embodiment of the present inventionwill be described below with reference to FIG. 7. FIG. 7 is a schematiccross-sectional view showing a cross-section of an exhaust gaspurification apparatus according to the second embodiment of the presentinvention cut parallel to the longitudinal direction.

In FIG. 7, exhaust gas is indicated by G₂. Further, the flow of theexhaust gas is indicated by arrows.

Note that in the second embodiment of the present invention, a honeycombfilter is used as an aggregated honeycomb structure.

As shown in FIG. 7, an exhaust gas purification apparatus 100 accordingto the second embodiment of the present invention includes: acylindrical casing 130; a cylindrical introduction pipe 120 a connectedto one end portion of the casing 130 and formed to taper in theneighborhood of a connection portion; an exhaust pipe 120 b connected tothe other end portion of the casing 130 and having a similarconfiguration to the introduction pipe 120 a; a honeycomb filter 140disposed in the casing 130; a holding sealing material 150 disposedbetween the honeycomb filter 140 and the casing 130; a buffer member 170disposed on an exhaust pipe side end face 140 a of the honeycomb filter140; a stopping member 160 disposed adjacent to the buffer member 170;and a fixing member 180 disposed adjacent to the stopping member 160 andjoined to the stopping member 160.

Note that the honeycomb filter 140, holding sealing material 150, buffermember 170, stopping member 160, and fixing member 180 disposed in thecasing will occasionally be referred to together as a purificationportion 190.

Next, the interior configuration of the exhaust gas purificationapparatus 100 according to the second embodiment of the presentinvention will be described.

In the exhaust gas purification apparatus 100, a distance (indicated bya double-headed arrow E in FIG. 7) between the exhaust pipe side endface 140 a of the honeycomb filter 140 and the end face of the stoppingmember 160 is less than about 1 mm.

Further, the stopping member 160 and the fixing member 180 are joined toeach other by welding a joint portion 160 b of the stopping member 160to the fixing member 180 (in FIG. 7, the welded part between the jointportion 160 b and the fixing member 180 is indicated by 161).

Further, the exhaust pipe 120 b is formed to taper toward an end face ona side connected to the outside, and a part of a peripheral portion ofthe fixing member 180 contacts the exhaust pipe 120 b. Thus, the fixingmember 180 does not move from its initial disposal position to theexhaust pipe 120 b side.

Furthermore, in the purification portion 190 disposed in the casing 130,the buffer member 170 is disposed to contact the entire exhaust pipeside end face 140 a of the honeycomb filter 140 (honeycomb fired body141), as shown in FIG. 7. The buffer member 170 is formed from a fiberbody having a plurality of air holes such that exhaust gas can passthrough.

A case in which exhaust gas is passed through the exhaust gaspurification apparatus 100 of the second embodiment of the presentinvention, configured as described above, will now be described.

Exhaust gas G₂ introduced through the introduction pipe 120 a flows intoone cell 145 that opens onto an end face 140 b of the honeycomb filter140 positioned on the introduction pipe side, and then passes through acell wall 146 separating the cell 145. At this time, PM contained in theexhaust gas is captured in the interior of the cell wall 146 such thatthe exhaust gas is purified. The purified exhaust gas then flows outfrom another cell 145 that opens onto the exhaust pipe side end face 140a. The effluent exhaust gas then passes through the buffer member 170and an opening 160 a in the stopping member 160 to be discharged to theoutside through the exhaust pipe 120 b.

During this exhaust gas purification process, pressure is applied to thehoneycomb filter 140 by the exhaust gas G₂.

Each member of the exhaust gas purification apparatus 100 describedabove will now be described in detail with reference to FIGS. 8A, 8B and9.

FIG. 8A is a schematic perspective view showing the buffer member of theexhaust gas purification apparatus according to the second embodiment ofthe present invention. FIG. 8B is a schematic perspective view showingthe fixing member of the exhaust gas purification apparatus according tothe second embodiment of the present invention.

FIG. 9 is a schematic perspective view showing a state in which thehoneycomb filter, the holding sealing material, the stopping member, andthe buffer member and fixing member shown in FIGS. 8A and 8B aredisposed in the casing to which the introduction pipe and exhaust pipeare connected.

The respective configurations of the honeycomb filter 140, casing 130,holding sealing material 150, stopping member 160, introduction pipe 120a, and exhaust pipe 120 b shown in FIG. 9 are described above in thedescription of the exhaust gas purification apparatus according to thefirst embodiment, and are therefore not described here.

First, the buffer member 170 will be described. As shown in FIG. 8A, thebuffer member 170 is a disc-shaped, sheet-form fiber body mainlyincluding inorganic fibers such as alumina fibers. The diameter of anend face of the buffer member 170 is substantially identical to theinner diameter of the casing 130 shown in FIG. 9, and the thickness isless than about 1 mm.

Next, the fixing member 180 will be described. As shown in FIG. 8B, thefixing member 180 mainly includes a metal such as stainless steel, andtakes a ring shape having a predetermined thickness. The outer diameterof the fixing member 180 is substantially identical to the innerdiameter of the casing 130 shown in FIG. 9, and the inner diameter isslightly larger than the diameter of the end face of the honeycombfilter 140 shown in FIG. 9.

A method for manufacturing the exhaust gas purification apparatusaccording to the second embodiment of the present invention will now bedescribed.

First, the honeycomb filter, casing, holding sealing material, stoppingmember, introduction pipe, and exhaust pipe are manufactured in asimilar manner to the method for manufacturing the exhaust gaspurification apparatus according to the first embodiment of the presentinvention.

Next, a mat material produced by a sheet-forming process of inorganicfibers mainly including alumina or the like is processed such that thediameter of an end face of the mat material is substantially identicalto the inner diameter of the casing and the thickness is less than about1 mm, whereby a buffer member including a sheet-form fiber body ismanufactured.

Next, a ring-shaped fixing member in which the outer diameter of an endface thereof is substantially identical to the inner diameter of thecasing and the inner diameter of the end face is slightly larger thanthe diameter of the end face of the honeycomb filter is manufactured bycarrying out a punching process on a disc-shaped metal plate mainlyincluding a metal such as stainless steel.

A method for manufacturing an exhaust gas purification apparatus usingthe honeycomb filter and the various members described above will now bedescribed.

First, the holding sealing material is wrapped around the periphery ofthe honeycomb filter such that the recessed portion and projectedportion of the holding sealing material are fitted together. Next, thefirst casing divided body is disposed such that the inner face thereofis oriented upward, and the honeycomb filter wrapped in the holdingsealing material is disposed on the inner face of the first casingdivided body. Further, the buffer member is disposed adjacent to one endface of the honeycomb filter. Next, the fixing member, which is joinedto the stopping member by carrying out welding at the joint portion, isdisposed such that the stopping member is adjacent to the buffer member.

Next, the second casing divided body is placed on the first casingdivided body in which the honeycomb filter and the respective membersdescribed above are disposed, whereupon the casing divided bodies arecompressed from a vertical direction. Once the casing divided bodieshave come into contact, the casing divided bodies are joined by weldingto form the casing. Note that a joining device such as a screw or apredetermined fitting may be used instead of welding.

Next, the exhaust pipe is connected to the end portion of the casingthat is positioned on the stopping member disposal side by welding.Similarly, the introduction pipe is connected to the end portion of thecasing on the opposite side to the exhaust pipe connection side.

Through the processes described above, the exhaust gas purificationapparatus according to the second embodiment of the present invention ismanufactured.

The effects (1) and (3) described in the first embodiment of the presentinvention are exhibited similarly in the second embodiment of thepresent invention.

The second embodiment also exhibits the following effects.

(4) In the exhaust gas purification apparatus according to the secondembodiment of the present invention, the fixing member for fixing thestopping member is disposed in a predetermined position in the casing.Therefore, the stopping member is unlikely to shift from its initialdisposal position.

Hence, even when exhaust gas pressure is applied to the honeycombfilter, movement of a honeycomb fired body from the honeycomb filter tothe exhaust pipe side is more likely to be prevented reliably.Furthermore, even if a honeycomb fired body moves, the moving honeycombfired body is stopped reliably upon contact with the stopping member.Therefore, displacement and drop of the honeycomb fired bodies are morelikely to be prevented efficiently.

(5) In the exhaust gas purification apparatus according to the secondembodiment of the present invention, the stopping member is joined tothe fixing member.

Therefore, the stopping member is unlikely to be displaced from itsinitial disposal position, and contact between the stopping member andthe honeycomb fired body is unlikely to occur.

Hence, damage such as chips and cracks is more likely to be preventedfrom occurring on the end face (exhaust pipe side end face) of thehoneycomb filter on which damage is particularly likely to occur.

As a result, a reduction in the purification performance of thehoneycomb filter is more likely to be prevented.

(6) In the exhaust gas purification apparatus according to the secondembodiment of the present invention, the exhaust pipe side end face ofthe honeycomb filter contacts the buffer member having a bufferingfunction, and therefore, even when the entire honeycomb filter movesfrom its initial disposal position to the exhaust pipe side due toexhaust gas pressure, shock such as vibration is unlikely to be appliedto the exhaust pipe side end face of the honeycomb filter. Hence, damageis more likely to be prevented from occurring on the end face (exhaustpipe side end face) of the honeycomb filter on which damage isparticularly likely to occur.

As a result, a reduction in the purification performance of thehoneycomb filter is more likely to be prevented efficiently.

Example 2 (1) Manufacture of Honeycomb Filter

The honeycomb filter was manufactured in a similar manner to (1) ofExample 1.

(2) Manufacture of Holding Sealing Material

The holding sealing material was manufactured in a similar manner to (2)of Example 1.

(3) Manufacture of Stopping Member

The stopping member was manufactured in a similar manner to (3) ofExample 1.

(4) Manufacture of Buffer Member

A mat material produced by a sheet-forming process of non-expansivealumina fibers was processed to a size of diameter 152 mm×thickness 0.5mm to manufacture a buffer member including a sheet-form fiber body.

(5) Manufacture of Fixing Member

A ring-shaped fixing member was manufactured to a size of outer diameter152 mm (inner diameter 142 mm)×thickness 4 mm by carrying out a punchingprocess on a disc-shaped stainless steel metal plate having a size ofdiameter 152 mm×thickness 4 mm.

(6) Manufacture of Exhaust Gas Purification Apparatus

The honeycomb filter wrapped in the holding sealing material wasdisposed on the inner face of the first casing divided body in a similarmanner to Process (4) of Example 1.

Next, the buffer member manufactured in Process (4) was disposed on theinner face of the first casing divided body adjacent to one end face ofthe honeycomb filter. Next, the fixing member was joined to the jointportion of the stopping member, whereupon the fixing member was disposedon the inner face of the first casing divided body such that thestopping member was adjacent to the buffer member.

The second casing divided body was then placed on the first casingdivided body provided with the honeycomb filter and stopping member,whereupon the casing divided bodies were compressed from a verticaldirection. When the casing divided bodies came into contact, the casingdivided bodies were joined by welding to form a casing.

Next, an exhaust pipe including stainless steel and formed in a taperedshape was disposed on the end portion of the casing on the stoppingmember disposal side, and connected to the end portion of the casing bywelding. Similarly, an introduction pipe shaped identically to theexhaust pipe was connected to the end portion of the casing on theopposite side to the exhaust pipe connection side.

Through the processes described above, the exhaust gas purificationapparatus according to the second embodiment was manufactured.

Note that in the exhaust gas purification apparatus manufactured in thismanner, the distance between the exhaust pipe side end face of thehoneycomb filter and the end face of the stopping member was 0.5 mm.

Further, the exhaust pipe was formed in a tapered form, and the fixingmember joined to the stopping member contacted a part of the exhaustpipe.

In the exhaust gas purification apparatus according to Example 2, theexhaust pipe side end face of the honeycomb filter is covered by thestopping member. It may therefore be assumed that even when exhaust gaspressure is applied, displacement and drop of the honeycomb fired bodiescan be prevented.

Further, the fixing member for fixing the stopping member is disposed ina predetermined position within the casing, and in addition, thestopping member is joined to the fixing member. It may therefore beassumed that the stopping member is unlikely to shift from its initialdisposal position, and that contact between the stopping member and thehoneycomb structure due to movement of the stopping member is unlikelyto occur.

Moreover, the distance between the end face of the honeycomb filter andthe end face of the stopping member is less than about 1 mm. It maytherefore be assumed that a reduction in the purification performance ofthe honeycomb filter can be prevented efficiently.

Third Embodiment

Next, a third embodiment serving as an embodiment of the presentinvention will be described.

In the third embodiment of the present invention, the stopping memberaccording to the exhaust gas purification apparatus of the secondembodiment of the present invention is not joined to the fixing member.

The effects (1) and (3) described in the first embodiment of the presentinvention and the effects (4) and (6) described in the second embodimentof the present invention are exhibited similarly in the thirdembodiment.

Fourth Embodiment

Next, a fourth embodiment serving as an embodiment of the presentinvention will be described using the drawings.

FIG. 10A is a schematic perspective view showing a casing and a fixingmember of an exhaust gas purification apparatus according to the fourthembodiment of the present invention, and FIG. 10B is a schematic sideview showing the casing and the fixing member shown in FIG. 1A.

In the fourth embodiment of the present invention, the fixing memberaccording to the exhaust gas purification apparatus of the secondembodiment of the present invention is formed from a plurality offittings formed mainly by a metal such as stainless steel. Morespecifically, as shown in FIGS. 10A and 10B, a fixing member 280 isformed from six fittings, which are welded in predetermined positionswithin a casing 230 (230 a and 230 b) along the inner periphery of thecasing 230 (230 a and 230 b) such that distances between the sixfittings are equal. Three fittings are disposed in each casing dividedbody 230 a (230 b).

Further, the fittings are joined to a stopping member (not shown) bywelding.

The effects (1) and (3) described in the first embodiment of the presentinvention and the effects (4) to (6) described in the second embodimentof the present invention are exhibited similarly in the fourthembodiment of the present invention.

Fifth Embodiment

Next, a fifth embodiment serving as an embodiment of the presentinvention will be described.

In the fifth embodiment of the present invention, a catalyst made ofplatinum or the like is supported on the honeycomb filter according tothe exhaust gas purification apparatus of the first embodiment of thepresent invention. Note that methods for supporting a catalyst on thehoneycomb filter include a method for immersing the honeycomb filter ina diamine dinitro platinum nitric acid ([Pt(NH₃)₂(NO₂)₂]HNO₃) solutionor the like and then heating the honeycomb filter, for example.

The effects (1), (2) and (3) described in the first embodiment of thepresent invention are exhibited similarly in the fifth embodiment of thepresent invention.

The fifth embodiment also exhibits the following effect.

(7) In the exhaust gas purification apparatus according to the fifthembodiment of the present invention, a honeycomb filter with a catalystsupported thereon is disposed in the casing.

Hence, by causing the PM captured in the honeycomb filter to contact thecatalyst, the captured PM is more likely to be burned at lowertemperatures. Therefore, in the exhaust gas purification apparatusaccording to the fifth embodiment of the present invention, PM containedin the exhaust gas is more likely to be removed efficiently.

Moreover, by causing the harmful gas components contained in the exhaustgas to contact the catalyst, the harmful gas components contained in theexhaust gas are more likely to be converted.

Sixth Embodiment

A sixth embodiment serving as an embodiment of the present inventionwill now be described.

In the sixth embodiment of the present invention, a casing is providedwith a purification portion formed by a catalyst supporting carrier inwhich the honeycomb filter according to the exhaust gas purificationapparatus of the second embodiment of the present invention is formedsuch that one of the end portions of each of the cells is not sealed, aholding sealing member disposed between the catalyst supporting carrierand the casing, a buffer member disposed on the exhaust pipe side endface of the catalyst supporting carrier, a stopping member disposedadjacent to the buffer member, and a fixing member disposed adjacent tothe stopping member and joined to the casing. Further, a catalyst issupported on the catalyst supporting carrier.

A method for manufacturing the catalyst supporting carrier according tothe exhaust gas purification apparatus of the sixth embodiment of thepresent invention will now be described.

First, inorganic particles such as alumina or silica particles,inorganic fibers such as alumina or silica fibers, and an inorganicbinder such as silica sol are mixed to prepare a wet mixture. Asnecessary and in accordance with formability, an organic binder such ascarboxymethyl cellulose, a dispersion medium such as water, a lubricantsuch as polyoxyethylene monobutyl ether, and a forming auxiliary such asethylene glycol are appropriately added thereto. Extrusion molding isthen carried out using the prepared wet mixture to manufacture a rawmolded body. The raw molded body is then dried to manufacture a ceramicdried body.

An aggregated honeycomb structure is then manufactured using a similarmethod to the method for manufacturing the honeycomb filter according tothe exhaust gas purification apparatus of the first embodiment of thepresent invention, except that predetermined cells of the ceramic driedbody are not sealed and the firing temperature is between at least about500° C. and at most about 1200° C.

The obtained aggregated honeycomb structure forms a catalyst supportingcarrier in which one of the end portions of each of the cells is notsealed.

Next, the catalyst supporting carrier is caused to support a catalystusing an identical method to the method for causing the honeycomb filteraccording to the exhaust gas purification apparatus of the fifthembodiment of the present invention to support a catalyst. Through theprocesses described above, the catalyst supporting carrier with acatalyst supported thereon is manufactured.

Note that an identical catalyst to the catalyst described in the fifthembodiment of the present invention may be used as the catalyst of thesixth embodiment of the present invention.

Effects of the exhaust gas purification apparatus according to the sixthembodiment of the present invention will be listed below.

(8) In the exhaust gas purification apparatus according to the sixthembodiment of the present invention, the catalyst supporting carrier isdisposed in the casing, with one of the end portions of each of thecells in the aggregated honeycomb structure not being sealed, and acatalyst is supported on the catalyst supporting carrier.

Hence, the exhaust gas purification apparatus according to the sixthembodiment of the present invention is more likely to be capable ofconverting harmful gas components contained in the exhaust gas.

(9) Furthermore, for similar reasons to those described in the effects(1) to (3) of the first embodiment of the present invention, the exhaustgas purification apparatus according to the sixth embodiment of thepresent invention is more likely to maintain high levels of PM captureefficiency and harmful gas component conversion efficiency over a longtime period.

Seventh Embodiment

Next, the interior configuration of an exhaust gas purificationapparatus according to a seventh embodiment serving as an embodiment ofthe present invention will be described with reference to FIG. 11.

FIG. 11 is a schematic cross-sectional view showing a cross-section ofthe exhaust gas purification apparatus according to the seventhembodiment of the present invention cut parallel to the longitudinaldirection.

As shown in FIG. 11, an exhaust gas purification apparatus 300 accordingto the seventh embodiment of the present invention includes a casing330, an introduction pipe 320 a, an exhaust pipe 320 b, and a firstpurification portion 390 and a second purification portion 190 disposedin the casing 330.

The interior configuration of the exhaust gas purification apparatus 300according to the seventh embodiment of the present invention will now bedescribed using the drawings.

As shown in FIG. 11, the first purification portion 390, which has anidentical configuration to the purification portion according to theexhaust gas purification apparatus of the sixth embodiment except that abuffer member is not provided and the stopping member is not joined tothe fixing member, is disposed on the introduction pipe 320 a side ofthe casing 330. More specifically, a catalyst supporting carrier 340, aholding sealing material 350 disposed between the catalyst supportingcarrier 340 and the casing 330, a stopping member 360 disposed on anexhaust pipe side end face 340 a of the catalyst supporting carrier 340,and a fixing member 380 disposed adjacent to the stopping member 360 areprovided in the first purification portion 390.

Further, the fixing member 380 is joined to the casing 330 by a screw, apredetermined fitting, or the like.

Meanwhile, the second purification portion 190, which has an identicalconfiguration to the purification portion according to the exhaust gaspurification apparatus of the second embodiment except that a buffermember is not provided and the stopping member is not joined to thefixing member, is disposed on the exhaust pipe 320 b side of the casing330. More specifically, a honeycomb filter 140, a holding sealingmaterial 150 disposed between the honeycomb filter 140 and the casing330, a stopping member 160 disposed on an exhaust pipe side end face 140a of the honeycomb filter 140, and a fixing member 180 disposed adjacentto the stopping member 160 are provided in the second purificationportion 190.

Further, the fixing member 180 is joined to the casing 330 by a screw, apredetermined fitting, or the like.

In the exhaust gas purification apparatus 300 of the seventh embodiment,having the configuration described above, exhaust gas (in FIG. 11, theexhaust gas is indicated by G₃, and the flow of the exhaust gas isindicated by arrows) introduced through the introduction pipe 320 apasses through the catalyst supporting carrier 340 and then passesthrough the honeycomb filter 140 to be discharged to the outside throughthe exhaust pipe 320 b.

During this exhaust gas purification process, pressure is applied to thecatalyst supporting carrier 340 and the honeycomb filter 140 by theexhaust gas G₃.

A method for manufacturing the exhaust gas purification apparatusaccording to the seventh embodiment of the present invention will now bedescribed.

First, a catalyst supporting carrier manufactured using a similar methodto the method for manufacturing the catalyst supporting carrieraccording to the exhaust gas purification apparatus of the sixthembodiment of the present invention and a honeycomb filter manufacturedusing a similar method to the method for manufacturing the honeycombfilter according to the exhaust gas purification apparatus of the firstembodiment of the present invention are prepared.

Next, the first purification portion is disposed on the inner face of afirst casing divided body in a similar manner to the second embodiment,except that the buffer member is not used and the fixing member andstopping member are not fixed.

Next, the second purification portion is disposed adjacent to the firstpurification portion in a similar manner to the second embodiment,except that the buffer member is not used and the fixing member andstopping member are not fixed. In this case, the second purificationportion is disposed such that an end face of the catalyst supportingcarrier of the first purification portion on the side where the variousmembers are disposed and an end face of the honeycomb filter of thesecond purification portion on the side where the various members aredisposed are oriented in an identical direction.

Next, a second casing divided body is placed on the casing divided bodyprovided with the catalyst supporting carrier, the honeycomb filter, andthe various members, whereupon the casing divided bodies are compressedfrom a vertical direction. Once the casing divided bodies have come intocontact, the casing divided bodies are joined by welding to form thecasing.

Note that a joining device such as a screw or a predetermined fittingmay be used instead of welding.

Next, the fixing member of the first purification portion and the fixingmember of the second purification portion are joined respectively to thecasing using a screw, a predetermined fitting, or the like.

Finally, the exhaust gas purification apparatus according to the seventhembodiment of the present invention is manufactured by carrying out asimilar connection process to that of the method for manufacturing theexhaust gas purification apparatus according to the second embodiment ofthe present invention.

In the exhaust gas purification apparatus according to the seventhembodiment manufactured in this manner, the first purification portion(catalyst supporting carrier) is positioned on the introduction pipeside. Further, the second purification portion (honeycomb filter) ispositioned on the exhaust pipe side, or in other words downstream of thecatalyst supporting carrier.

Effects of the exhaust gas purification apparatus according to theseventh embodiment of the present invention will be listed below.

In the exhaust gas purification apparatus according to the seventhembodiment of the present invention, a purification portion having anidentical configuration to the purification portion of the sixthembodiment, except that the buffer member is not provided and thestopping member and fixing member are not joined, is used as the firstpurification portion, and therefore the effects (8) and (9) described inthe sixth embodiment are exhibited.

Further, a purification portion having an identical configuration to thepurification portion of the second embodiment of the present invention,except that the buffer member is not provided and the stopping memberand fixing member are not joined, is used as the second purificationportion, and therefore the effect (4) described in the second embodimentof the present invention are exhibited.

Moreover, the following effects can be exhibited.

(10) In the exhaust gas purification apparatus according to the seventhembodiment of the present invention, from among the end faces of thecatalyst supporting carrier of the first purification portion and thehoneycomb filter of the second purification portion, the end facespositioned on the respective exhaust pipe sides are covered by thestopping members.

Hence, a part of the honeycomb fired bodies of the catalyst supportingcarrier is not pushed out to the exhaust pipe side when exhaust gaspressure is applied. As a result, the honeycomb fired bodies areunlikely to collide with the honeycomb filter disposed downstream of thecatalyst supporting carrier, and damage to the entire honeycomb filteris more likely to be prevented.

Thus, a reduction in the purification performance of the honeycombfilter is more likely to be prevented.

(11) In the exhaust gas purification apparatus according to the seventhembodiment of the present invention, the catalyst supporting carrier isdisposed further toward the introduction pipe side than the honeycombfilter.

Therefore, heat generated when the catalyst supporting carrier convertsharmful gas components contained in the exhaust gas can be used easilyduring PM combustion in the honeycomb filter positioned downstream ofthe catalyst supporting carrier. As a result, PM contained in theexhaust gas is more likely to be removed extremely efficiently.

Other Embodiments

The stopping member of the exhaust gas purification apparatus accordingto the embodiment of the present invention is preferably formed by amaterial that is unlikely to be eroded by a flow of exhaust gas.

Specifically, this material is not limited to the above-describedstainless steel, and includes carbon steel, titanium, iron, aluminum,and so on. When the stopping member includes carbon steel, nickelplating is preferably carried out on the surface of the stopping member.

When a stopping member including wire mesh is used as the stoppingmember, the type of the wire mesh is not limited to the above-describedplain weave wire mesh, and instead, twill weave wire mesh, crimped wiremesh, lock-crimped wire mesh, ton-cap weave wire mesh, ty-rod weave wiremesh, and so on, for example, may be used.

The stopping member is not limited to the above-described wire mesh, andmay be a punching metal or the like formed by carrying out a punchingprocess on a metal plate, for example, to form openings (round holes) ofa predetermined size over substantially the entire end face.

Further, the openings formed in the punching metal are not limited tothe above-described round holes, and may be square holes, hexagonalholes, rectangular holes, elongated round holes, rhombic holes, crossholes, combination of round holes and cross holes, and so on. Moreover,the openings are not limited to the above-described straightarrangement, and may be formed in an about 60° staggered arrangement, anabout 45° staggered arrangement, and so on.

There are no particular limitations on the shape of the fixing member ofthe exhaust gas purification apparatus according to the embodiment ofthe present invention, and instead of the above-described ring shape, anL shape or the like may be used. In this case, a plurality of fixingmembers are preferably disposed in the casing so that the stoppingmember is more likely to be fixed more rigidly.

There are no particular limitations on the materials of the casing,fixing member and introduction pipe of the exhaust gas purificationapparatus according to the embodiment of the present invention, andinstead of the above-described stainless steel, metals such as aluminumand iron, for example, may be used.

The casing of the exhaust gas purification apparatus according to theembodiment of the present invention is not limited to a cylindricalshape, and may take any tubular shape, such as an elliptical shape, atriangular shape, a hexagonal shape, an octagonal shape, or adodecagonal shape, when seen from above.

Further, the cylindrical casing may be a cylindrical casing that isdivided into a plurality of pieces along the longitudinal direction(i.e. a clam shell-type casing) or a cylindrical casing having aC-shaped or U-shaped cross-section in which a slit (opening portion)extending in the longitudinal direction is formed in only one location.

The shape of the stopping member, and the shape of the buffer member andfixing member provided as necessary, may be modified appropriately inaccordance with the shape of the casing.

The main component of the material of the honeycomb filter is notlimited to silicon carbide, and may be another ceramic raw material, forexample a nitride ceramic such as aluminum nitride, silicon nitride,boron nitride, or titanium nitride, a carbide ceramic such as zirconiumcarbide, titanium carbide, tantalum carbide, or tungsten carbide, acomplex of a metal and nitride ceramic, a complex of a metal and carbideceramic, and the like.

Further, a ceramic raw material such as a silicon-containing ceramic, inwhich metal silicon is mixed with the above-described ceramics, and aceramic joined by silicon or a silicate compound may also be used as thematerial of the honeycomb filter.

The inorganic particles included in the material of the catalystsupporting carrier are not limited to the above-described inorganicparticles including alumina or silica, and may be inorganic particlesincluding zirconia, titania, ceria, mullite, zeolite, and so on. Theseinorganic particles may be used singly or in combinations of two or morekinds. Of these kinds, inorganic particles including alumina and ceriaare particularly preferable.

The inorganic fibers included in the material of the catalyst supportingcarrier is not limited to the above-described inorganic fibers includingalumina or silica, and may be inorganic fibers or whiskers includingsilicon carbide, silica-alumina, glass, potassium titanate, aluminumborate, and so on. These may be used singly or in combinations of two ormore kinds. Of the above-described inorganic fibers, inorganic fibersincluding aluminum borate whiskers are preferable.

Note that in this description, the inorganic fibers and whiskers areassumed to have an aspect ratio (length/diameter) of more than 5. Theaspect ratio of the inorganic fibers and whiskers is preferably at leastabout 10 and at most about 1000.

There are no particular limitations on firing conditions whenmanufacturing the catalyst supporting carrier, but preferably at leastabout 500° C. and at most about 1200° C., and more preferably in therange of about 600° C. to about 1000° C.

The reason for this is that when the firing temperature is about 500° C.or more, the adhesive function of the inorganic binder is more likely toappear and sintering of the inorganic particles and the like is morelikely to advance, so that a reduction in the strength of the honeycombfired body is less likely to occur. When the firing temperature is about1200° C. or less, sintering of the inorganic particles and the like isless likely to advance excessively, so that a reduction in specificsurface area per unit volume is less likely to occur. As a result, thecatalyst component supported on the catalyst supporting carrier when ahoneycomb structure including honeycomb fired bodies is used as thecatalyst supporting carrier for converting the exhaust gas is morelikely to be dispersed to a sufficiently high degree.

The catalyst supporting carrier may have a catalytic function.

In addition to the above described catalyst supporting carrier to whicha catalytic function is provided by supporting a catalyst on a catalystsupporting carrier (honeycomb structure) not having a catalyticfunction, examples of the catalyst supporting carrier having a catalyticfunction may include a catalyst supporting carrier produced by using amaterial having a catalytic function such as ceria and aluminum so thatthe catalyst supporting carrier (honeycomb structure) has a catalyticfunction in itself.

The aggregated honeycomb structure (unless otherwise indicated, it isassumed in the following description that the aggregated honeycombstructure includes a honeycomb filter and a catalyst supporting carrier)of the exhaust gas purification apparatus according to the embodiment ofthe present invention is not limited to a round pillar shape, and maytake any pillar shape such as a cylindroid shape or a polygonal pillarshape.

The catalyst supported on the aggregated honeycomb structure of theexhaust gas purification apparatus according to the embodiment of thepresent invention is not limited to the above-described platinumcatalyst, and a noble metal such as palladium or rhodium, an alkalimetal such as potassium or sodium, an alkaline-earth metal such asbarium, or a metal oxide, for example, may be used instead. Thesecatalysts may be used singly or in combinations of two or more kinds.

Further, there are no particular limitations on the above-describedmetal oxide as long as it is capable of reducing the combustiontemperature of the PM, and a composite oxide represented by CeO₂, ZrO₂,FeO₂, Fe₂O₃, CuO, CuO₂, Mn₂O₃, MnO, the composition formula AnB_(1-n)CO₃(in the formula, A is La, Nd, Sm, Eu, Gd or Y, B is an alkali metal oralkaline-earth metal, and C is Mn, Co, Fe or Ni) or the like, forexample, may be used instead.

These metal oxides may be used singly or in combinations of two or morekinds, and a metal oxide containing at least CeO₂ is preferable.

When this kind of metal oxide is supported, the combustion temperatureof the PM is more likely to be reduced.

As a method for supporting a catalyst on the aggregated honeycombstructure, a method for forming a catalyst supporting layer including analumina film on the surface of the aggregated honeycomb structure andsupporting a catalyst on the alumina film or the like may be employedinstead of the above-described method for immersing the aggregatedhoneycomb structure in a solution containing a catalyst and then heatingthe aggregated honeycomb structure.

Examples of methods for forming an alumina film include a method forimmersing the aggregated honeycomb structure in a metallic compoundsolution containing aluminum, such as Al(NO₃)₃, and then heating theaggregated honeycomb structure, and a method for immersing theaggregated honeycomb structure in a solution containing alumina powderand then heating the aggregated honeycomb structure.

Further, examples of methods for supporting a catalyst on the aluminafilm include a method for immersing the aggregated honeycomb structureformed with the alumina film in a solution containing a noble metal, analkali metal, an alkaline-earth metal, or a metal oxide, or the like,and then heating the aggregated honeycomb structure.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

1. An exhaust gas purification apparatus comprising: at least onehoneycomb structure comprising: a plurality of honeycomb fired bodieswhich are bound together via an adhesive layer and each of whichincludes cell walls extending along a longitudinal direction of the atleast one honeycomb structure to define cells; an introduction end face;and an exhaust end face opposite to the introduction end face in thelongitudinal direction; a casing housing said at least one honeycombstructure and comprising: an introduction casing end face connected toan introduction pipe to introduce an exhaust gas; and an exhaust casingend face connected to an exhaust pipe to discharge the exhaust gas, theintroduction end face of the at least one honeycomb structure facing theintroduction casing end face, the exhaust end face of the at least onehoneycomb structure facing the exhaust casing end face; a holdingsealing material disposed between said at least one honeycomb structureand said casing to hold said at least one honeycomb structure; and astopping member having a plurality of openings and disposed in saidcasing, said stopping member covering the exhaust end face of the atleast one honeycomb structure.
 2. The exhaust gas purification apparatusaccording to claim 1, further comprising: a fixing member disposed insaid casing to fix said stopping member.
 3. The exhaust gas purificationapparatus according to claim 2, wherein said fixing member has a ringshape.
 4. The exhaust gas purification apparatus according to claim 2,wherein said fixing member comprises a plurality of fittings.
 5. Theexhaust gas purification apparatus according to claim 4, wherein saidplurality of fittings are welded in said casing along an inner peripherythereof such that distances between respective fittings aresubstantially equal.
 6. The exhaust gas purification apparatus accordingto claim 2, wherein said fixing member has an L shape.
 7. The exhaustgas purification apparatus according to claim 2, Wherein said stoppingmember is joined to said fixing member.
 8. The exhaust gas purificationapparatus according to claim 2, wherein said stopping member is notjoined to said fixing member.
 9. The exhaust gas purification apparatusaccording to claim 1, wherein said stopping member comprises a wiremesh.
 10. The exhaust gas purification apparatus according to claim 1,wherein said stopping member comprises a punching metal.
 11. The exhaustgas purification apparatus according to claim 1, wherein said stoppingmember has an aperture ratio of at least about 65% and at most about95%.
 12. The exhaust gas purification apparatus according to claim 11,wherein said stopping member has an aperture ratio of at least about 70%and at most about 90%.
 13. The exhaust gas purification apparatusaccording to claim 1, wherein said stopping member comprises at leastone of stainless steel, carbon steel, titanium, iron and aluminum. 14.The exhaust gas purification apparatus according to claim 1, whereinsaid stopping member is joined to said casing.
 15. The exhaust gaspurification apparatus according to claim 1, further comprising: abuffer member disposed between said at least one honeycomb structure andsaid stopping member.
 16. The exhaust gas purification apparatusaccording to claim 15, wherein said buffer member comprises a sheet-formfiber body comprising inorganic fibers.
 17. The exhaust gas purificationapparatus according to claim 1, wherein a distance between the exhaustend face of said at least one honeycomb structure and an end face ofsaid stopping member is less than about 1 mm.
 18. The exhaust gaspurification apparatus according to claim 1, wherein a catalyst issupported on said at least one honeycomb structure.
 19. The exhaust gaspurification apparatus according to claim 18, wherein said catalystcomprises at least one of a noble metal, an alkali metal, analkaline-earth metal and a metal oxide.
 20. The exhaust gas purificationapparatus according to claim 1, wherein said at least one honeycombstructure is a honeycomb filter in which one of end portions of each ofsaid cells is sealed.
 21. The exhaust gas purification apparatusaccording to claim 20, wherein a catalyst is supported on said honeycombfilter.
 22. The exhaust gas purification apparatus according to claim21, wherein said catalyst comprises at least one of a noble metal, analkali metal, an alkaline-earth metal and a metal oxide.
 23. The exhaustgas purification apparatus according to claim 20, wherein said honeycombfilter comprises at least one of a nitride ceramic, a carbide ceramic, acomplex of a metal and a nitride ceramic, and a complex of a metal and acarbide ceramic.
 24. The exhaust gas purification apparatus according toclaim 20, wherein said honeycomb filter comprises a silicon containingceramic in which at least one of a nitride ceramic, a carbide ceramic, acomplex of a metal and a nitride ceramic, and a complex of a metal and acarbide ceramic is blended with a metal silicon.
 25. The exhaust gaspurification apparatus according to claim 20, wherein said honeycombfilter comprises a ceramic in which at least one of a nitride ceramic, acarbide ceramic, a complex of a metal and a nitride ceramic, and acomplex of a metal and a carbide ceramic is combined by one of a siliconand a silicate compound.
 26. The exhaust gas purification apparatusaccording to claim 1, wherein said at least one honeycomb structure is acatalyst supporting carrier in which said one of end portions of each ofsaid cells is not sealed.
 27. The exhaust gas purification apparatusaccording to claim 26, wherein a catalyst is supported on said catalystsupporting carrier.
 28. The exhaust gas purification apparatus accordingto claim 27, wherein said catalyst comprises at least one of a noblemetal, an alkali metal, an alkaline-earth metal and a metal oxide. 29.The exhaust gas purification apparatus according to claim 26, whereinsaid catalyst supporting carrier comprises inorganic particles,inorganic fibers and an inorganic binder.
 30. The exhaust gaspurification apparatus according to claim 29, wherein said inorganicparticles comprise at least one of alumina, silica, zirconia, titania,ceria, mullite and zeolite.
 31. The exhaust gas purification apparatusaccording to claim 29, wherein said inorganic fibers comprise at leastone of alumina, silica, silicon carbide, silica-alumina, glass,potassium titanate and aluminum borate.
 32. The exhaust gas purificationapparatus according to claim 26, wherein said catalyst supportingcarrier has a catalytic function.
 33. The exhaust gas purificationapparatus according to claim 32, wherein a catalyst is supported on saidcatalyst supporting carrier.
 34. The exhaust gas purification apparatusaccording to claim 1, wherein the at least one honeycomb structurecomprises a plurality of honeycomb structures.
 35. The exhaust gaspurification apparatus according to claim 34, wherein a distance betweenthe exhaust end face of each of said honeycomb structures and an endface of said stopping member is less than about 1 mm.
 36. The exhaustgas purification apparatus according to claim 34, wherein said pluralityof honeycomb structures include at least one honeycomb filter and atleast one catalyst supporting carrier, and said catalyst supportingcarrier is disposed between the introduction casing end face and saidhoneycomb filter.
 37. The exhaust gas purification apparatus accordingto claim 36, wherein a catalyst is supported on said honeycomb filter.38. The exhaust gas purification apparatus according to claim 37,wherein said catalyst comprises at least one of a noble metal, an alkalimetal, an alkaline-earth metal and a metal oxide.
 39. The exhaust gaspurification apparatus according to claim 36, wherein said honeycombfilter comprises at least one of a nitride ceramic, a carbide ceramic, acomplex of a metal and a nitride ceramic, and a complex of a metal and acarbide ceramic.
 40. The exhaust gas purification apparatus according toclaim 36, wherein said honeycomb filter comprises a silicon containingceramic in which at least one of a nitride ceramic, a carbide ceramic, acomplex of a metal and a nitride ceramic, and a complex of a metal and acarbide ceramic is blended with a metal silicon.
 41. The exhaust gaspurification apparatus according to claim 36, wherein said honeycombfilter comprises a ceramic in which at least one of a nitride ceramic, acarbide ceramic, a complex of a metal and a nitride ceramic, and acomplex of a metal and a carbide ceramic is combined by one of a siliconand a silicate compound.
 42. The exhaust gas purification apparatusaccording to claim 36, wherein a catalyst is supported on said catalystsupporting carrier.
 43. The exhaust gas purification apparatus accordingto claim 42, wherein said catalyst is at least one of a noble metal, analkali metal, an alkaline-earth metal and a metal oxide.
 44. The exhaustgas purification apparatus according to claim 36, wherein said catalystsupporting carrier comprises inorganic particles, inorganic fibers andan inorganic binder.
 45. The exhaust gas purification apparatusaccording to claim 44, wherein said inorganic particles comprise atleast one of alumina, silica, zirconia, titania, ceria, mullite andzeolite.
 46. The exhaust gas purification apparatus according to claim44, wherein said inorganic fibers comprise at least one of alumina,silica, silicon carbide, silica-alumina, glass, potassium titanate andaluminum borate.
 47. The exhaust gas purification apparatus according toclaim 36, wherein said catalyst supporting carrier has a catalyticfunction.
 48. The exhaust gas purification apparatus according to claim47, wherein a catalyst is supported on said catalyst supporting carrier.